Image acquisition devices project a three-dimensional scene onto a two-dimensional sensor. During operation, a conventional capture device captures a two-dimensional (2-D) image of the scene representing an amount of light that reaches a photosensor (or photodetector or photosite) within the device. However, this 2-D image contains no information about the directional distribution of the light rays that reach the photosensor, which may be referred to as the light-field. Depth, for example, is lost during the acquisition. Thus, a conventional capture device does not store most of the information about the light distribution from the scene.
Light-field capture devices, also referred to as “light-field data acquisition devices”, have been designed to measure a four-dimensional (4D) light-field of the scene by capturing the light from different viewpoints of that scene. Thus, by measuring the amount of light traveling along each beam of light that intersects the photosensor, these devices can capture additional optical information, in particular information about the directional distribution of the bundle of light rays, for providing new imaging applications by post-processing. The information acquired/obtained by a light-field capture device is referred to as the light-field data. Light-field capture devices are defined herein as any devices that are capable of capturing light-field data. There are several types of light-field capture devices, among which:                plenoptic devices, which use a microlens array placed between the image sensor and the main lens, as described in document US 2013/0222633;        a camera array, as described by Wilburn et al. in “High performance imaging using large camera arrays.” ACM Transactions on Graphics (TOG) 24, no. 3 (2005): 765-776 and in patent document U.S. Pat. No. 8,514,491 B2.        
Light-field data processing comprises notably, but is not limited to, generating refocused images of a scene, generating perspective views of a scene, generating depth maps of a scene, generating extended depth of field (EDOF) images, generating stereoscopic images, and/or any combination of these.
Images or videos acquired by light-field acquisition devices may need to be transmitted to other devices, for example to display devices.
When the user wants to display the light-field content on its display device, he/she may select different portions of the content to bring different portions of the content into focus and out of focus. The focus plane is set at the desired depth, and the depth data is used to refocus the portions of the image selected by the user.
However, the picture synthesized accordingly may lack realism and aesthetic quality. Actually, out-of-focus parts of an image produced by a lens are blurred. The aesthetic quality of such a blur is called bokeh, which may be defined as “the way the lens renders out-of-focus points of light”. Differences in lens aberrations and aperture shape cause some lens designs to blur the image in a way that is pleasing to the eye, while others produce blurring that is unpleasant or distracting.
When rendering an image or a video from a light-field content, it would be interesting to display an image as close as possible as a conventional image or video in terms of blur aesthetics, i.e. to display an image with good bokeh properties.
It would hence be desirable to provide a technique for encoding and decoding a signal representative of a light-field content, which would be appropriate to the specificities of light-field imaging, and which would allow realistic and/or aesthetic rendering of image or video contents.
The present invention has been devised with the foregoing in mind.